Category: SETI

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To date, SETI (Search for ExtraTerrestrial Intelligence) has focused on ETs who ‘phone home’ using the radio part of the electromagnetic spectrum, and even a very small region within that.

But what if ET’s phone doesn’t use radio waves? Sure the xkcd comic, is funny, but maybe it points to a deep flaw in our attempts to contact, or hear from, an ETI?

When Giuseppe Cocconi and Philip Morrison suggested the possibility of interstellar communication via electromagnetic waves in a 1959 paper in Nature, only radio was feasible, as we then had the ability to detect only artificial radio signals, if produced by ETIs with 1959 human technology. Since then we’ve developed the ability to detect a laser signal, brighter than the Sun (if only for a nanosecond) if it came from a source several light-years away … but lasers weren’t invented then.

What might ET’s equivalent of ants’ pheromones be?

Back in 1959 if you’d said that the Earth would, within a mere half century, started to go ‘radio quiet’, not many people would have taken you seriously. Yet that’s exactly what’s happened! Free to air (FTA) broadcasting, especially for TV, is being replaced by TV delivered over coaxial cable, optical fibers, or even the phone company’s twisted copper pairs. And where it’s continuing, as in satellite TV broadcasting, its power has dropped (today’s digital formats are more efficient than the old analog ones). Military radars, the brightest source of artificial radio waves by far, no longer broadcast in a single channel, but hop, rapidly, from frequency to frequency, to avoid jamming.

“Our improving technology is causing the Earth to become less visible,” says astronomer Frank Drake, SETI’s paterfamilias. “If we are the model for the universe, that is bad news.”

In the past half century SETI researchers have expanded the scope of their searches. Not only are far more radio channels being examined, but artificial signals in the optical are being sought too. How to decide which of the billions or trillions of possible radio channels to search? For example, the Allen Telescope Array will, when built, monitor a billion channels between 0.5 and 11 GHz – but that’s a trivial fraction of the entire radio waveband. Some ideas, however, seem cute; for example, the SETI Institute’s Gerald Harp has proposed searching at 4.462336275 gigahertz, in what’s called the PiHI range, because it’s the hydrogen atom’s emission frequency times pi. More seriously, Harvard University’s Paul Horowitz says optical SETI programs should really look at infrared frequencies “Stars are darker in the infrared and lasers are brighter and the smog goes away,” Horowitz says. Infrared allows astronomers to see into the galactic center, where dust scatters visible light.

There’s something rather ironic about SETI today; on the one hand, we recognize that our initial hopes were far too high, being based on overly simplistic assumptions; on the other, the tremendous progress in finding exoplanets has given us greater and greater certainty that Earth-like planets not only exist, but are, very likely, common. “All of astronomy has come to embrace this idea that there must be life out there,” says Harp.

So how to address the fact that we simply do not know what sorts of technologies a civilization like ours may have, a century or a millennium from now? After all, as Drake says “We are very conservative at SETI, we assume in our searches the existence of only things we ourselves have and know how to make.” Other scientists, and SETI enthusiasts, have proposed hunting in different electromagnetic realms, like gamma rays. Spacecraft that rely on nuclear fusion or antimatter-matter annihilation as a power source might produce such rays. But standard SETI strategy does not embrace such “speculative” scenarios.

SETI researchers, some say, should also contemplate what technologies supersmart aliens might possess and seek out the corresponding signals. In a 2008 arXiv paper, “Galactic Neutrino Communication“, John Learned of the University of Hawaii at Manoa suggested that ET could be sending beams of neutrinos Earth’s way. Energy requirements for such a beam make that scenario seem implausible, but not necessarily impossible. Detectors currently under construction, such as IceCube at the South Pole, could spot unexpected stray neutrinos. If a few with the same energy came from the same direction, astronomers would know something screwy was up.

In another paper, “The Cepheid Galactic Internet“, Learned suggests that ET could send a signal using a neutrino beam to deliver energy to a Cepheid variable. A Cepheid “blows up and comes crashing back down,” he says. “And the energy builds up and it blows again, like a geyser.” ET could leverage a Cepheid’s inherent instability by delivering a boost of energy that messes with the star’s schedule. Looking through existing data could reveal whether such meddling has occurred. “All that is needed is people analyzing for other reasons to do their analyses in another way,” Learned says.

Drake and most others agree that SETI’s approach should be multidirectional – let a thousand alien hunters bloom. The only ideas that don’t do anybody any good, Horowitz says, are the ones for which there is no conceivable way to look. “I’d like to keep an open mind,” he says, “but not so much that my brain falls out.”

Physicist Paul Davies of Arizona State University in Tempe, however, suggests that researchers don’t need to know what to look for. Find the fishy thing first, and then argue about its origin, he says.

As Davies has argued, maybe discovering ET does indeed depend on a thought revolution. Fifty years of signal-less searching suggests that the problem could lie not with the aliens among the stars, but with ourselves.

Maybe the sentient ants should not give up, just yet.

Sources: Science News. Cocconi and Morrison’s 1959 Nature paper (copyright Nature)

While having lunch with colleagues at Los Alamos National Labs in 1950, physicist Enrico Fermi mused about the likelihood of intelligent life existing elsewhere in the Universe.  Fermi, one of the most astute scientists of his day, thought the size and age of the Universe means many advanced civilizations should have already colonized the galaxy, just as humans colonized and explored the Earth.   But if such galaxy-wide extraterrestrial civilizations exist, he wondered, where are they?

Some believe this problem, called the Fermi Paradox, means advanced extraterrestrial societies are rare or nonexistent.  Others suggest they must destroy themselves before they move on to the stars.

But this week, Jacob D. Haqq-Misra and Seth D. Baum at Penn State University proposed another solution to the Fermi Paradox: that extraterrestrial civilizations haven’t colonized the galaxy because the exponential growth of a civilization required to do so is unsustainable.

The researchers call their idea the “Sustainability Solution”.  It states: “The absence of ETI (extra-terrestrial intelligence) observation can be explained by the possibility that exponential or other faster growth is not a sustainable development pattern for intelligent civilizations.”

The researchers base their conclusions on a study of civilizations on Earth.  Historically, rapid growth of societies means rapid resource depletion and environmental degradation, usually with dire results.  They cite the example of Easter Island, where resource depletion likely caused a collapse of the local population.  And they conclude that while there are examples of sustainable growth like the !Kung San people of the Kalahari Desert, exponential growth in population and spatial expansion of a society is almost always linked to unsustainable growth and eventual collapse.

This principle has implications for our current global civilization.  Since Earth’s resources are finite and it receives solar radiation at a constant rate, human civilization cannot sustain an indefinite, exponential growth.  But even if we survive and advance as a civilization, we may have trouble colonizing the galaxy should we ever decide to do so.  And if this limitation applies to us, it may apply to other civilizations as well.

But the Sustainability Solution doesn’t mean ET is not out there.  Slower-growth extraterrestrial societies might still communicate by radio or other wavelengths, so current SETI programs still make sense.  Or ETI may result in chemical bio-markers in planetary atmospheres which may leave spectroscopic signatures detectable with upcoming generations of Earth and space-based planet-hunting telescopes.

The Sustainability Solution also allows that advanced civilizations may indeed colonize the galaxy, then collapse as resources are consumed at an unsustainable rate.

And some civilizations may send small messenger probes to other stars, which suggests a search for extraterrestrial artifacts (SETA) within our own solar system might be just as fruitful as radio-based SETI.  Searches might involve radio or visible detection of extraterrestrial probes orbiting the sun.  Or artifacts may even be embedded within planets or moons of our solar system, just like the giant black monoliths in Arthur C. Clarke’s 2001: A Space Odyssey.

In any case, the discovery of artifacts from a slow-growth extraterrestrial civilization would be an example “sustainable development” on a galactic scale.

You can read the original article here.